textproduct: Quad Cities

KEY MESSAGES

- Active pattern to continue into the weekend with numerous rounds of showers and storms including heavy rainfall at times.

- There is Marginal Risk, Level 1 out of 5, for severe storms in west-central Illinois and south of Highway 34 this afternoon/evening. Isolated damaging winds is the primary hazard.

- An elevated flash flooding risk could develop mid-week with repeating rounds of storms. There is a medium to high chance (40-75%) for portions of eastern Iowa to see over 2 inches of rainfall, with localized areas of 4+ inches possible (5-10%), leading to rises on area creeks and streams.

SHORT TERM /THROUGH THURSDAY/

Issued at 259 AM CDT Tue Sep 15 2026

Widespread showers and storms (80-100%) are expected this morning along a cold front, mainly north of Highway 34. With the shortwave trough and mid-latitude cyclone over south-central Canada lifting to the northeast, a lot of the dynamical support for the ongoing showers and storms will be lost, so the coverage and intensity will gradually decrease throughout today, especially north of I-80. Heading into tonight, the cold front is forecasted to stall out over northern Missouri, keeping scattered PoPs (30-60%) around south of I-80, as lows drop back into the mid-50s and low 60s with the return to northeasterly flow. There will be a short period late this afternoon/evening where storms that develop along the cloud-enhanced theta-e gradient could tap into 750-1250 J/kg of SBCAPE in west-central Illinois and south of Highway 34. The SPC has highlighted this area with a Marginal Risk, Level 1 out of 5, for severe storms with isolated damaging winds as the primary hazard.

On Wednesday, a shortwave over the western CONUS will become cut off from the main flow and pull weak disturbances in the jet stream northward from the subtropics. With the stationary front providing surface lift and the residual mid-level moisture from today's system, more scattered showers and storms (50-70% coverage) are likely to redevelop along and north of this boundary and persist into Wednesday night. If storms on Wednesday track over the same areas that received over 1-2 inches of rainfall today, the flash flood risk could become elevated, and this is noted by the WPC's Slight Risk, Level 2 out of 4, for excessive rainfall areawide. By Thursday, a lobe of mid-level vorticity moves into the central Rockies as surface cyclogenesis occurs across eastern Colorado. While storm coverage will be lower on Thursday (20-40%), the stationary front across northern Missouri is forecast to convert into a warm front, setting the stage for a wet start to the weekend.

In total through Thursday evening, rainfall totals will likely (70-100%) range from 1-3 inches areawide outside of our far southeast counties in west-central Illinois and northeast Missouri. While these numbers are slightly lower than previously forecasted, there is still a low chance (5-10%) for localized areas across eastern Iowa to see 4+ inches of rainfall which could lead to rises on small creeks and streams.

LONG TERM /THURSDAY NIGHT THROUGH MONDAY/

Issued at 259 AM CDT Tue Sep 15 2026

Friday-Saturday...The mid-level trough moves into the Dakotas and Minnesota, dragging the Colorado low with it towards Iowa. A WAA wing will likely develop along the warm front moving into our CWA and force more scattered storms (50-70% coverage). Muggy conditions are likely (60-90%) to return Friday into Saturday with dew points back into the upper 60s and 70s areawide. By Saturday, the low pressure slowly meanders across the Upper Mississippi River Valley as another round of scattered storms (40-70% coverage) is forecast to form from the enhanced surface convergence.

Sunday-Monday...The trough over the western CONUS finally ejects eastward into the Northern Plain on Sunday, introducing the upper- level flow needed to kick the low pressure sitting over the region eastward towards the Great Lakes. With the return to northerly surface flow/dry air advection on the backside of this low, PoPs should decrease on Sunday with Monday likely (80-95% chance) being the first area-wide dry day in over a week as seasonable conditions resume!

AVIATION /12Z TAFS THROUGH 12Z WEDNESDAY/

Issued at 629 AM CDT Tue Sep 15 2026

MVFR/IFR conditions expected through the morning hours with vsby reductions due to showers/isolated thunderstorms. Kept thunder mention at MLI for the next couple hours until risk wanes with weakening LLJ. A cold front to track through late morning turning winds northwesterly along with some lowering MVFR/brief IFR cigs at CID/DBQ. Additional showers and isolated storms are possible across southeast IA late this afternoon and evening and have maintained/adjusted PROB30 mention for thunder at BRL. Some guidance hints at lower cigs moving into BRL late in the period and have trended the TAF in this direction.

DVN WATCHES/WARNINGS/ADVISORIES

IA...None. IL...None. MO...None.